Orsellinic acid

• 2,4-dihydroxy- 6-methyl- benzoic acid
• O- orsellinic
• 6-methyl- β - resorcylic acid
• 4,6- dihydroxy -o- toluic

Colorless needles

Fixed

176 ° C ( decomposition)

Soluble in ethanol and ether

Hydrate

Attention

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The orsellinic acid is an organic acid and is derived from benzoic acid by adding two hydroxy groups, and a methyl group as a substituent are added. It belongs therefore, inter alia, to the group of phenolic acids. It also is close to the subgroup of dihydroxybenzoic acids and differs concretely from the β - resorcylic (2,4- dihydroxybenzoic acid ) by an added methyl group. It plays a role in the biochemistry of the braiding and of Aspergillus and Penicillium strains from which they can be isolated. The biosynthesis in these organisms proceeds via the polyketide pathway.

Occurrence and biosynthesis

Orsellinic arises, inter alia, as a secondary metabolite in Aspergillus nidulans. The formation of orsellinic can be specifically triggered by the close, physical contact with neighboring bacteria or a mutation in Signalosome complex. Orsellinic, orcinol and penicillin acid can be found in cultures of Penicillium fennelliae. It plays a role in the biochemistry of lichens from which they can be isolated.

The biosynthesis proceeds via the polyketide pathway, is established in which, from simple, coenzyme A- activated acyl groups (usually acetyl -CoA ), a tetraketide and then cyclized.

For A. nidulans the gene for a orsellinic synthase (OAS ) has been identified that is similar to a typical non-reducing polyketide synthase. The sequence information is evidence of different domains that play a role in the biosynthetic pathway. So you have identified sequence motifs of a starting acyltransferase, a ketosynthase, an acyltransferase, a Produkttemplatdomäne, an acyl carrier protein and thioesterase. Thus it is believed that from three molecules of malonyl -CoA and an enzyme-bound acetyl -CoA, a molecule orsellinic can be formed. Acetyl -CoA is used as the starting molecule for the synthesis, all other steps are enzyme- bound instead.

Representation

The synthesis is achieved by Michael addition of ethyl acetoacetate to crotonic followed by an intramolecular Claisen condensation. Here, Dihydroorsellinsäureethylester forms. Dehydration and ester cleavage lead to orsellinic.

Orsellinic acid can also be prepared by oxidation of Orcylaldehyd.

It can be also shown when you Everninsäure ( CAS: 570-10-5 ) and Ramalsäure ( CAS: 500-37-8 ) is heated with barium hydroxide and thus cleaves the ester bond.

A further synthesis starts from orcinol, which is carboxylated with magnesium methyl carbonate in DMF.

Properties

Orsellinic acid forms colorless crystals in the form of needles. It decomposes on rapid heating at 176 ° C and decarboxylated while orcinol.